Y'golonac was created by Ramsey Campbell in "Cold Print" (1969). It manifests as a bloated, headless humanoid figure with a toothed mouth set into each palm, and it presides over depravity and perverse desire. Reading its name in a cursed text is sufficient to summon it.
The entity typically possesses a human host to act in the world, selecting individuals suited to corrupt others on its behalf. It is regarded as one of the Mythos figures that most directly embodies the danger of forbidden, voyeuristic knowledge.